Generation and sorting of two kinds of composite vortex beams

An optical vortex beam carrying orbital angular momentum (OAM) is characterized by a phase singularity at its beam axis, and has attracted more and more attention in the fields of large-capacity optical communication, holographic storage, laser processing, high-resolution imaging, and quantum information. Composite vortex beams with multiple orbital angular momentum modes are usually used as the light resources in these applications. In this study, two kinds of composite vortex beams have been generated and sorted, which are respectively superimposed by orthogonally polarized states and coherent states. The orthogonally polarized superimposed vortex beam is generated by using a configuration composed of a vortex retarder and two quarter-wave plates, while the coherent superimposed vortex beam is generated by using a configuration composed of a vortex retarder and a polarizer. Furthermore, the OAM spectrums of superimposed vortex beams have been measured using an optical geometric transformation. We demonstrate that the OAM spectrums of the orthogonally polarized superimposed vortex beams can be regulated by controlling the polarization of the incident beams, while the OAM spectrums of the coherent superimposed vortex beams cannot. Our results might provide some significant references for the applications in optical communication and quantum information using superimposed vortex beams in the near future.